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    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        a:link{
            display: block;
            width: 93px;
            height: 29px;
            background-image: url("./img/09/btn.png");
        }
        a:hover{
            background-image: url("./img/09/btn.png");
        }
        a:active{
            background-image: url("./img/09/btn.png");
        }

        /* 
            图片属于网页中的外部资源，外部资源都需要浏览器单独发送请求加载，
            浏览器加载外部资源时是按需加载的，用则加载，不用则不加载
            像我们上边的练习link会首先加载，而hover和active会在指定状态触发时才会加载
            
        */
    </style>
</head>
<body>
    <a href="javascript:;"></a>
</body>
</html>